[tools] Add version_converter deprecation warning

Re-added 'odml.tools.version_converter.py' that imports the
'VersionConverter' class from its new location 'odml.tools.converters'
and prints a deprecation warning. This ensures backwards compatibility
with dependent tools like odml-ui during a grace period.

Author: mpsonntag

odml/tools/version_converter.py

@@ -0,0 +1,5 @@
+from .converters import VersionConverter
+
+print("[DEPRECATION WARNING] The VersionConverter file has been moved to "
+      "'odml.tools.converters' and will be removed from 'odml.tools' in future "
+      "odML releases. Please update the imports in your code accordingly.")